Geometric phase in entangled systems: A single-neutron interferometer experiment

S. Sponar, J. Klepp, R. Loidl, S. Filipp, K. Durstberger-Rennhofer, R. A. Bertlmann, G. Badurek, H. Rauch, Y. Hasegawa

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Abstract

The influence of the geometric phase on a Bell measurement, as proposed by Bertlmann [Phys. Rev. A 69, 032112 (2004)] and expressed by the Clauser-Horne-Shimony-Holt (CHSH) inequality, has been observed for a spin-path-entangled neutron state in an interferometric setup. It is experimentally demonstrated that the effect of geometric phase can be balanced by a change in Bell angles. The geometric phase is acquired during a time-dependent interaction with a radiofrequency field. Two schemes, polar and azimuthal adjustment of the Bell angles, are realized and analyzed in detail. The former scheme yields a sinusoidal oscillation of the correlation function S, dependent on the geometric phase, such that it varies in the range between 2 and 2√2 and therefore always exceeds the boundary value 2 between quantum mechanic and noncontextual theories. The latter scheme results in a constant, maximal violation of the Bell-like CHSH inequality, where S remains 2√2 for all settings of the geometric phase.

Original languageEnglish
Article number042113
JournalPhysical Review A
Volume81
Issue number4
DOIs
StatePublished - 30 Apr 2010
Externally publishedYes

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